Food mixer with screw-threaded impeller

ABSTRACT

A screw-threaded impeller  50  having a mixing device  55  thereon is provided in a container  10  of a food processor. A drive unit adjacent the bottom of the container is adapted to move the impeller in both a clockwise and a counterclockwise direction. During rotation, food placed within the container is lifted away from the mixing device when the impeller is rotated in one direction and is directed toward the mixing device when the impeller is rotated in the other direction. The mixing device includes a horizontal cutting blade  52  extending perpendicular to the impeller and a scooping blade  51  extending downwardly at an angle from the impeller. In order to lift over obstacles, the mixing device is spring mounted or can move along the helical protrusion toward the upper end of the impeller.

“This application is a Continuation of Ser. No. 09/508,291, filed Mar.30, 2000, which is a 371 of PCT/AU98/00734, filed Sep. 9, 1998.”

This invention relates to the area of food processing and in particularto a food mixer or blender capable of carrying out various foodprocessing functions more efficiently than previous such mixers.

BACKGROUND TO THE INVENTION

Most food mixers are based on pairs of beaters which rotate aboutparallel axes so that the beater heads inter-engage and the materialbeing mixed tends to pass between the heads.

In some other applications, where heavier materials are being beaten orkneaded, a single blade is used and this blade may either be shaped asin a dough hook or have a surface which is open and through and aroundwhich the material being mixed passes. Such mixers and blenders howeverare usually not particularly efficient at breaking up flour lumps andsuch like and do not homogenise mixtures in a safe and splash free way.In particular most mixers do not readily blend small amounts ofsubstances such as mayonnaise.

Most mixers also become sluggish in their movement as more ingredientsare added and the contents of the mixer become more viscous.Additionally, chopper type blades in such mixers tend to have a crushingeffect on materials added, such as chocolate chips, and do not providean even consistency.

It is an object of this invention to provide a mixer which permitseffective mixing of food products while minimising the problems outlinedabove.

OUTLINE OF THE INVENTION

The mixer of the invention uses a single impeller, rather than the twinbeater concept, which is adapted to drive various mixing devices asappropriate.

The invention in its broadest sense is a food mixer which includes acontainer having an impeller adapted to be driven by drive meansadjacent the lower surface of the container and which impeller isadapted both to cooperate with various mixing devices and to rotate ineither the clockwise or anti-clockwise direction.

It is preferred that the impeller be centrally mounted within asubstantially symmetrical container however the container itself may beof any desired shape. It is also preferred that the impeller be able tobe driven in both the clockwise and anti-clockwise directions.

In one embodiment of the invention it may be preferred that the impelleris a relatively short tubular shaped member with a mixing memberattached thereto with the upper end of the impeller being provided witha dome shaped cap with a dimpled or serrated lower surface which aids inbreaking up food lumps remaining once the food has been cut, orotherwise processed, and which also helps reduce the possibility ofcontact between implements inserted in the container and any cuttingmeans used. This cap also assists in minimising splash and enhancing thelateral spread of ingredients during mixing.

It is however preferred that the mixer be provided with central impellershafts which may extend up to any height in the container and which canbe provided with mixing or other devices as required.

In order that the invention may be more readily understood embodimentsof it by way of non limiting example will be described here withreference to the following diagrams:

FIG. 1 shows the invention fitted with a hybrid chopper device and aninterior lid to adjust for different quantities of foodstuffs;

FIG. 2 shows an embodiment of the invention with a threaded centralimpeller and a mixing device;

FIG. 3 shows an embodiment of the invention in which the impeller isprovided with a whisking device and an inside lid;

FIG. 4 shows an embodiment of the invention in which the impeller isfitted with a cap which may shield a cutting or mixing device below it;

Considering first the embodiment of the invention shown in FIG. 1. Acontainer 10 is provided with a central impeller shaft 20 which can bedriven from below the lower surface of the substantially cylindricalcontainer 10. A hybrid chopper/blade device 30 is also provided whichcan be passed over the central shaft until adjacent the lower face ofthe container.

While in general the central impeller shaft may extend up to any heightinside the container in this embodiment it extends the full height ofthe container which may be closed with an optional lid 70 if it isdesired that a funnelled opening 80 be provided for the insertion offood material.

The arrangement of the chopper/blade assembly 30 is such that apreferably plastic scooping blade 31 extends at an angle to the verticalfrom the centre of one side of the device and terminates at thecontainer edge, the lower edge of the blade 31 being parallel to andjust slightly above the lower inside edge of the container.

On the opposite side of the impeller shaft from the scooping blade thedevice is provided with an essentially horizontal preferably arcuateshaped chopping blade 32, preferably of metal, which in a preferredembodiment has a face which cuts or chops when the impeller shaft isrotated clockwise but does not chop when it is rotated anticlockwise.

The sense of rotation is not however a restriction on the inventiveconcept nor need the blade be sharp on only one side and it is envisagedthat a useful embodiment of the invention may be provided by a cuttingaction when the rotation was in reverse.

This combination of a scooping blade 31 used in combination with achopping blade 32 dramatically improves the mixer's ability to cut hardvegetables evenly.

If it is desired that aeration be provided as well as mixing the bladesdescribed can either be roughened in some manner or be perforated withholes. In practice I have found the latter method to produce the bestresults.

It is also envisaged that the mixing and chopping blades of thisinvention be able, if required, to move up and down the central shaft byway of a groove 33 in the shaft, with the chopper assembly's up and downmovement being largely determined by the sense of rotation of theimpeller, or be located at different heights within the container byfixing the mixing assembly being used at some chosen height via the useof at least one fastening device locating on the central shaft.

The chopper/blade assembly 30 is preferably used (as shown in FIG. 1) incombination with a deflector disc 40 which can be slid down over theimpeller shaft above the chopper blade.

This deflector disc 40 is basically an annulus which covers the internalarea of the container and acts as an effective inside lid.

The arrangement is such that the hub 41 of the disc is slid over theupper part of the impeller in sufficient proximity to the impeller toallow the deflector disc to be oriented at right angles to the containerwall while freely allowing the impeller shaft 20 to rotate within acentral aperture in the hub and the disc. This aperture needs to besufficiently large to avoid any grooves on the impeller shaft.

Vertical grooves are provided in the interior wall of the centralportion of the hub to allow for the release of any pressure build-upunder the deflector disc when blending hot ingredients. This featurealso allows the user to drain off any excess liquid from a mixturewithout first having to remove the contents.

The function of the deflector disc is that it restricts the ingredientsto be mixed to the lower part of the container and prevents them beingspread to areas of the container where they cannot be further processed.

This action is particularly useful when a mixture of liquids and solidsis being blended and prevents splashing. In addition it acts to deflectfood particles flung up by the scooper blade into the path of the cutterblade and directs them back down to the cutter blade again.

It may also be preferred that the underside of the deflector disc beserrated or otherwise roughened to further aid in breaking up lumps offood.

Although the deflector disc can be made from any appropriate material,in this preferred embodiment it is made of a transparent material sothat the contents of the mixer are not obscured.

The perimeter of the disc may also be provided with a rim of siliconerubber or other appropriate material to maintain close contact with thecontainer wall if that is desired, alternately it may be a loose fit asshown in FIG. 3 to allow food material to pass into the lower part ofthe container or to allow the disc to “float” above the food materialbeing mixed while the weight of the hub could act to confine theingredients to the minimum space required.

Whatever method is used) the disc, while fitting firmly within thecontainer, should still be able to move in the vertical sufficiently toaccommodate expansion of the mixture being processed.

Although the deflector disc used in combination with the chopper bladeis highly efficient, certain combinations of ingredients can still bindtogether in such a way that they Ad deposit in positions within thecontainer which avoid the blades. For this reason the direction ofrotation of the chopper blade combination is able to be reversed,preferably slowly, so that the contents of the mixer can be agitated orstirred without being chopped. This feature is desirable not only forproviding even mixing but for stirring in additional material when nofurther chopping action is required.

In a further embodiment of the invention (FIG. 2) a scoop/paddle device55 is provided which comprises a set of plastic mixing paddles. Theseare similar in shape to the chopper/blade device previously describedhowever the essentially horizontal “blade” 52 is symmetrical about itscenterline and the scooping paddle 51 is quite flexible to allow doughs,and other mixes which may become compacted, to pass beneath it. It isalso further envisaged that the assembly could be spring mounted so asto lift over obstacles.

In this embodiment of the invention the scoop/paddle device 55 islocated about a spiral threaded screw impeller device 50 such that whenthe impeller is driven clockwise there is a downward screwing action onthe material, or dough, being kneaded such that the dough is gentlyforced down onto the paddles causing it to roll around the containerbetween its walls and the central impeller and provide gentle kneading.

While various devices can be used in conjunction with the spiralimpeller it has been my experience that, when the spiral impeller isdriven through an epicyclic gear set at about 300 rpm, its motion issufficiently slow as to not damage implements or fingers which may beinserted into the container and also that there is no need for a lid tocontain the dough.

In this embodiment of the invention the scoop/paddle device functions intwo ways dependant on the sense of rotation of the impeller.

When running in a counterclockwise direction the ingredients are liftedinto the path of the essentially horizontal paddle 52 thus aeratingflour and such and evenly distributing fat into the mixture for lightfluffy pastries.

With conventionally shaped blades some mixtures have a tendency tocompact in such a way that the blades cease to have any effect. However,when the impeller of the invention is driven in a counterclockwisedirection the mixture is churned up and the mixing action resumes.

The sense of rotation could of course be reversed using a nonconventionally threaded impeller however the above described arrangementis preferred.

In a further embodiment of the invention shown in FIG. 3 a centralimpeller 20 is provided with whisk devices 60 which are used for lightmixture whipping of food materials such as egg whites. In thisembodiment it is preferred that the disc 40 (or inner lid) be used toassist in spreading the food ingredients laterally and to help preventsplashing.

Another embodiment of the invention (FIG. 4) provides a short impeller20, which may be provided with any mixing device at its base, at the topof which is a dome shaped cap 90 which has several functions. One ofthese is to cover any food processing device and protect it from contactwith implements inserted into the container. Another is to aid in thelateral spread of food products being processed.

Another feature of this cap 90 is that its lower face is dimpled orserrated in order to aid in the breaking up of lumps of food once thatfood has been otherwise processed.

It can be seen that there are many possible applications for the conceptof the invention and that, while I have described herein variousembodiments of the invention, any combination or variation in thefeatures of the invention previously described lie within the concept ofthe invention.

What is claimed is:
 1. A food mixer comprising: (a) a container having abottom end and an open top end; (b) a drive means adjacent the bottomend; (c) a rotatable impeller vertically positioned within the containerand including a first end engaging the drive means, a second endextending toward the container top end, and a helical thread extendingfrom the first end to the second end on an outer surface of theimpeller; and (d) a spring mounted mixing device positioned on theimpeller and adapted to move vertically toward said second end to liftover obstacles while rotating with the impeller, wherein the drive meansis adapted to rotate the impeller in both a first direction and a seconddirection opposite the first direction, and further wherein food placedwithin the container is lifted away from the mixing device when theimpeller is rotated in the first direction and is directed toward themixing device when the impeller is rotated in the second direction. 2.The food mixer of claim 1 wherein the impeller is a substantiallycylindrically shaped member mounted within the container which issubstantially symmetrically shaped.
 3. The food mixer of claim 1,wherein the mixing device is a scoop/paddle device located on theimpeller adjacent to a lower surface of the container.
 4. The food mixerof claim 3, wherein the scoop/paddle device can rotate along the helicalthread of the impeller.
 5. An accessory for a food processing device,comprising: (a) a rotatable, cylindrical impeller including a first end,a second end and a helical threaded protrusion extending from the firstend to the second end on an outer surface of the impeller, wherein thefirst end is adapted to engage a drive at the bottom of a container ofthe food processing device when the impeller is vertically positionedtherein; and (b) a spring mounted mixing device positioned on theimpeller and adapted to move vertically toward said second end to liftover obstacles while rotating with the impeller, the mixing deviceincluding a horizontal cutting blade extending perpendicular to theimpeller and a scooping blade extending at an angle from the impeller,wherein the impeller is adapted to be rotated in both a clockwise and acounterclockwise direction by the food processing device, such that foodplaced within the container is lifted away from the mixing device whenthe impeller is rotated in one of the clockwise direction and thecounterclockwise direction and is directed toward the mixing device whenthe impeller is rotated in the other of the counterclockwise directionand the clockwise direction.
 6. The accessory of claim 5, wherein thescooping blade is flexible to allow food which may be compacted to passtherebeneath.
 7. A food processing device, comprising: a base housinghaving a motor and motor controls; a bidirectional drive unit coupledwith the motor; a container, selectively interlocked with the basehousing, so that the drive unit protrudes into the container; a lidadapted to interlock with the container; and an accessory, having arotatable, cylindrical impeller including a first end, a second end anda helical threaded protrusion extending from the first end to the secondend on an outer surface of the impeller, wherein the first end isadapted to engage the drive unit at a bottom of the container of theprocessing device when the impeller is vertically position therein; anda spring mounted mixing device positioned on the impeller and adapted tomove vertically toward said second end to lift over obstacles whilerotating with the impeller, the mixing device including a horizontalcutting blade extending perpendicular to the impeller and a scoopingblade extending at an angle from the impeller.
 8. A food processingdevice as recited in claim 7, wherein a bottom surface of thecylindrical impeller has a cavity to engage the drive unit.
 9. A foodprocessing device as recited in claim 7, wherein the helical threadedprotrusion is adapted to create a downward screwing action upon foodbeing kneaded such that the food is forced onto the cutting blade andthe scooping blade when the cylindrical impeller rotates in a firstdirection.
 10. A device as recited in claim 7, wherein the helicalthreaded protrusion is adapted to create a lifting and aerating actionupon food being processed when the cylindrical impeller rotates in afirst direction.
 11. A food mixer comprising: (a) a container having abottom and an open top end; (b) a drive means adjacent the bottom end;(c) a rotatable impeller vertically positioned within the container andincluding a first end engaging the drive means, a second end extendingtoward the container top end, and a helical thread extending from thefirst end to the second end on an outer surface of the impeller; and (d)a mixing device positioned on the impeller, said mixing device beingadapted to move vertically toward said second end and along said helicalthread to lift over obstacles while rotating about the impeller, whereinthe drive means is adapted to rotate the impeller in both a firstdirection and a second direction opposite the first direction, andfurther wherein food placed within the container is urged away from themixing device when the impeller is rotated in the first direction and isdirected toward the mixing device when the impeller is rotated in thesecond direction.
 12. An accessory for a food processing device,comprising: (a) a rotatable, cylindrical impeller including a first end,a second end and a helical threaded protrusion extending from the firstend to the second end on an outer surface of the impeller, wherein thefirst end is adapted to engage a drive at the bottom of a container ofthe food processing device when the impeller is vertically positiontherein; and (b) a spring mounted mixing device positioned on theimpeller, at least a portion of said mixing device being adapted to movevertically toward said second end to lift over obstacles while rotatingwith the impeller, the mixing device including a horizontal cuttingblade extending perpendicular to the impeller and a scooping bladeextending downwardly at an angle from the impeller, said scooping bladebeing flexible and having a high portion and a low portion adapted toscoop under food, wherein the impeller is adapted to be rotated in botha clockwise and a counterclockwise direction by the food processingdevice, such that food placed within the container is lifted away fromthe mixing device when the impeller is rotated in one of the clockwisedirection and the counterclockwise direction and is directed toward themixing device when the impeller is rotated in the other of thecounterclockwise direction and the clockwise direction.
 13. A foodprocessing device, comprising: a base housing having a motor and motorcontrols; a bidirectional drive unit coupled with the motor; acontainer, that can be selectively interlocked with the base housing, sothat the drive unit protrudes into the container; a lid adapted tointerlock with the container; and an accessory, having a rotatable,cylindrical impeller including a first end, a second end and a helicalthreaded protrusion extending from the first end to the second end on anouter surface of the impeller, wherein the first end is adapted toengage the drive at the bottom of the container of the processing devicewhen the impeller is vertically position therein; and a spring mountedmixing device positioned on the impeller, at least a portion of saidmixing device being adapted to move vertically toward said second end tolift over food while rotating with the impeller, the mixing deviceincluding a horizontal cutting blade extending perpendicular to theimpeller and a scooping blade extending downwardly at an angle from theimpeller, said scooping blade being flexible and having a high portionand a low portion adapted to scoop under food.